仅对MySQL表记录中首次出现的字符执行搜索/替换？
您可以通过CONCAT()withREPLACE()函数的帮助来实现。要查找首次出现的情况，您需要使用INSTR()函数。
语法如下-
UPDATE yourTableName SET UserPost = CONCAT(REPLACE(LEFT(yourColumnName, INSTR(yourColumnName, 'k')), 'k', 'i'), SUBSTRING(yourColumnName, INSTR(yourColumnName, 'k') + 1));
为了理解上述语法，让我们创建一个表。创建表的查询如下-
mysql> create table UserInformation -> ( -> UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> UserName varchar(10), -> UserPost text -> );
现在，您可以使用insert命令在表中插入一些记录。查询如下-
mysql> insert into UserInformation(UserName,UserPost) values('Larry','Thks is a MySQL query');
mysql> insert into UserInformation(UserName,UserPost) values('Mike','Thks is not a java program');
mysql> insert into UserInformation(UserName,UserPost) values('Sam','Thks is a SQL syntax');使用select语句显示表中的所有记录。查询如下-
mysql> select *from UserInformation;
以下是输出-
+--------+----------+----------------------------+ | UserId | UserName | UserPost | +--------+----------+----------------------------+ | 1 | Larry | Thks is a MySQL query | | 2 | Mike | Thks is not a java program | | 3 | Sam | Thks is a SQL syntax | +--------+----------+----------------------------+ 3 rows in set (0.00 sec)
这是要搜索/替换的查询，但只有第一次在记录中出现一个值。在这里，第一次出现的'k'被替换为'i'-
mysql> update UserInformation -> set UserPost=CONCAT(REPLACE(LEFT(UserPost, INSTR(UserPost, 'k')), 'k', 'i'), -> SUBSTRING(UserPost, INSTR(UserPost, 'k') + 1)); Rows matched: 3 Changed: 3 Warnings: 0
再次显示表中的所有记录。查询如下-
mysql> select *from UserInformation;
以下是显示用'I'代替的'k'第一次出现的输出-
+--------+----------+----------------------------+ | UserId | UserName | UserPost | +--------+----------+----------------------------+ | 1 | Larry | This is a MySQL query | | 2 | Mike | This is not a java program | | 3 | Sam | This is a SQL syntax | +--------+----------+----------------------------+ 3 rows in set (0.00 sec)